DC-DC power converters are used in many power management and supply applications, including, for example, power supply for portable devices such as laptop computers, cell phones, PDAs and the like. In power management and supply applications efficiency of the converter is an important parameter. In power supply applications for portable devices, for example, better efficiency results in longer battery life and/or a smaller battery. Thus, it is desirable to improve the efficiency of a power converter.
In a method according to the present invention, the power supply of the gate driver is split into two distinct power voltages with different values (Vcc and PVcc). This improves driver speed without adding gate charge losses, and hence improves the efficiency.
In a preferred method according to the present invention, the driver of the power stage receives power from two voltage sources, one supplying a higher voltage and the other supplying a lower voltage. Thus, the driver will produce two output voltages, one lower than the other.
According to one aspect of the present invention the lower output voltage is used to drive the gate of the switch in a power stage of the converter having the larger gate to source capacitance in order to reduce losses. Thus, in the preferred embodiment, the lower output voltage of the driver is used to drive the synchronous FET of a buck converter, which is typically the switch having the larger gate to source capacitance, thereby reducing power loss.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.